One problem is that it creates moral hazard, but that's an abstract theoretical issue for the EU to deal with down the road.

The more immediate problem is the PIIGS.

Here's how Dennis Gartman put it in a recent note:

If some resolution to the Greek Problem is achieved…either through German/French support or via the IMF …then it is but a matter of time until Portugal, Spain, Italy et al raise their hands individually or collectively and ask, “What about us?” Therein lies the problem. The Greek problem, when all is said and done, is on its own resolvable. All that must needs happen is for the German government to put a clothespin on its metaphorical nose so it cannot smell the bad odor of what it may chose to do and accept the “exceptional circumstances” clause of Article 122 of the Lisbon Treaty and bail Athens out. But Germany knows that Portugal, Spain, Italy et al are right behind Greece and will follow hard upon. Bonn bailed out Berlin, but will Bonn really want to bail out Athens… Lisbon…Madrid… Rome… and then Ankara, Sophia and others in the near future and the far?

UBS floor guy Art Cashin adds in today's note:

As Dennis perfectly puts it, the EU must find a mechanism, in fact, a ruse, to allow it to rescue Greece without violating its own “constitution”. Further, it must deal with a long list of other potential rescuees. It’s like Bear, Fannie, Freddie and Lehman on a sovereign basis. This may be a tough Spring – that’s if Spring ever arrives.